Finders/Keepers or..?
Wouldn't a B17 technically still belong to the US government? Just because it's old doesn't mean it's not still theirs does it? Can't imagine the Oz government being too happy if one of our current RAAF planes ended up in a swamp and the PNG museum or whoever sold it a "warbird enthusiast".
Or did the US Army Air Force have a grand sell off of all crashed/destroyed aircraft "as is, where is"?